Method for sterilizing containers

ABSTRACT

In a method for sterilizing a container, a valve body (30) is supported by a gas chamber (24) which is under atmospheric pressure. As a result when a pressure difference is present a static condition arises and keeps the valve open or closed. The valve can be used in a variety of way as influx or admission valve or condensate drain valve or as vacuum or condensate drain valve. The control method effects that in each phase the effective valve is kept open also after reaching the negative or positive peak pressure value until the pressure in the autoclave has adjusted itself to a predetermined closing switching pressure.

Sterilizing containers are used to accommodate clinical sterile materialwhich must be subjected to a steam sterilization. Said sterilizationtakes place in sterilizers which operate either by the gravitationmethod (flow method) or in modern equipment increasingly by a vacuummethod in which firstly one or more vacuum phases are provided toextract the air from the container, whereafter the container interior isexposed to a steam atmosphere under elevated pressure and elevatedtemperature, the sterilizing material thereby being subjected to asterilization. It is advantageous to drain condensate forming so thatthe material is available as dry as possible after the sterilization.After the steam sterilization time the container is subjected to afurther vacuum treatment to withdraw the sterilization steam with anyremaining condensate from the container.

To permit the medium exchange the sterilizing containers are eitherequipped with filters allowing a medium exchange but preventingrecontamination or valves are disposed in the container wall which closeafter the pressure exchange is completed. As influx or vacuum valvescheck valves according to DE 217,551 or a double valve according to DE1,217,550 are frequently used. As condensate draining valve bi-metalvalves have established themselves which have the advantage over purecheck valves that an opening of the valve for draining the condensatecan take place throughout the entire sterilizing stage.

A valve which can carry out all these functions is known from U.S. Pat.No. 4,228,914. In this case the gas chamber acting on the valve body isfilled with steam during the steam influx phase and at the end of thesteam influx phase, i.e. at the start of the sterilization time, theinflux opening to the gas chamber is sealed via a shrink hose so that onthe subsequent pressure reduction expansion of the gas chamber caneffect closure of the valve. This construction requires that after eachsterilizing operation the shrink hose must be replaced to ensure thesealing function. The sealing function cannot be effected properly ifthe shrink hose does not establish a reliable seal. If a leakage flowtakes place at the influx opening the seal is jeopardized because thepressure difference necessary for the closure pressure cannot form.

The invention overcomes the problem of providing an operationally safevalve system which operates reliably automatically without addition andsetting of parts and can be used in a variety of ways.

Due to the fact that the gas volume remains permanently in the chamberand need not be replenished on each sterilizing operation as in theprior art a reliable and leak-flow-free seal can be achieved in simplemanner, and said gas volume can be introduced under a defined pressureat predetermined temperature, in particular under atmospheric pressure,thereby ensuring reliable operation. Conveniently, the differentialpressure valve function is subjected to a spring bias, the valve openingor closing operation thereby being displaced somewhat with respect tothe atmospheric line. This is however admissible and desirable and thetemperature-induced pressure differences within the gas chamber can becompensated adequately as regards the desired function.

The particular difference of the invention compared with conventionalcheck valves resides in that in this case the control force is not thepressure difference acting on the valve disc but a force resulting fromthe compression or elongation of a pressure pickup (roll diaphragms,diaphragms, concertina hose, corrugated tube, pressure cylinder,barometer cam, etc.) which effects the valve stroke via control rods,control cams, levers, or alternatively (preferably) directly. Thedecisive part for the opening and closure condition of the valve istherefore played by the pressure present in the sterilizing chamber andnot the presence (absence) of a pressure difference at the valve itself.The control force generated by the pressure pickup can be furtherintensified by supplementing (replacing) part of the gas pressure springor all of said spring by liquid (preferably water) whose boiling pointis set to the desired switching point (usually about 100° C.) This thengives a combination of pressure-dependent and temperature-dependentcontrol.

The valve according to the invention may be used as influx valve forcontrolling the influx gas jet or as vacuum valve for extracting thesteam and finally the valve may also be used as condensate drain valve.

By appropriate valve configuration and arrangement it can be ensuredthat after the last vacuum phase the container is not completelyventilated again so that the container content is subjected to a vacuumuntil made available in the operating theater, the penetration of air onopening container showing that said vacuum remained present until saidopening.

Other features and advantages of the present invention will becomeapparent from the following description of preferred embodiments of theinvention, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a sterilizing container withvalves constructed according to the invention;

FIG. 2 is a partially broken away longitudinal section of thesterilizing container of FIG. 1;

FIG. 3 to FIG. 11 show various examples of valves which can be used inconjunction with a sterilizing container according to FIGS. 1 and 2;

FIG. 12 is a diagram showing a possible time-dependent pressurevariation during a sterilizing cycle together with the valve function ofthe individual valves;

FIG. 13 is a schematic view of a double valve constructed according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a sterilizing container of the design described in DE3,146,349. Said sterilizing container comprises a container lowerportion 10, a container cover 12 and an intermediate cover 14 carried bythe latter. The intermediate cover 14 is sealed with respect to theupper edge of the container lower portion 10 via a sealing ring 16. Thecover 12 is detachably secured to the container lower portion 10 viaclamp fasteners 18, the intermediate cover 14 thereby being sealinglybiased against the lower portion 10 via the supports 19 carrying theintermediate cover 14. The intermediate cover 14 is equipped with valves20 which are only indicated schematically in FIGS. 1 and 2. As apparentfrom FIG. 1 the bottom of the container lower portion 10 dropsdownwardly from all sides towards the center where a further valve 22indicated only schematically in FIGS. 1 and 2 is arranged which canserve as condensate drain. Said valves 20 and 22 form the subject of theinvention and are illustrated in various examples of embodiment of theinvention in FIGS. 3 to 11. Said valves can be used in sterilizingcontainers of a great variety of types and their use is not restrictedto the embodiment illustrated in FIGS 1 and 2. In particular, the valves20 may be arranged in a container cover fitted sealingly on thecontainer lower portion or alternatively in the container lower portion.

Common to all the embodiments is a gas chamber 24 which is sealed allround and bordered at least partially by resilient walls and in which apredetermined gas volume under predetermined pressure, preferably dryair under atmospheric pressure, is enclosed. All the valves arerotation-symmetrical with respect to a center axis 26. In all theexample (apart from the embodiment of FIG. 4) one of the opposingcircular chamber walls 28 carries a valve body in the form of anencircling sealing bead or sealing edge 30 which in the rest state bearson the container wall portion 32 which forms the valve seat. Within thesurface portion surrounded by the sealing bead 30 the wall portion 32 isprovided with passage holes 34 serving for the exchange of the media.

The chamber wall 28 is stiffened by an inwardly disposed plate 36 ofmetal or plastic. The opposite chamber wall 38 is likewise stiffened bya plate 40. The cylindrical side wall 42 between the front wall 28 andthe rear wall 38 is flexible in such a manner that the spacing betweenthe front and rear wall is variable depending on the pressuredifferences obtaining. Said side wall can be made in the manner of abellows or concertina and the chamber wall can be made in one piece orconsist of several parts which are joined sealingly together. Thestiffening plates 36 and 40 also serve as spring plates for a biasinghelical spring 44 disposed therebetween which pushes the two walls 28,38 apart and tends to increase the chamber volume. The gas chamber issurrounded by a housing 46 which is provided with openings and which isriveted to the wall portion 32 or otherwise secured. The rear wall 38can be connected to the housing 46 for example by riveting.

In all the examples the gas pressure of the chamber acts directly on thevalve bodies. This has the advantage that the valves can be accommodatedcompactly on the container wall. If considered expedient in specificcases the gas pressure chamber can also be arranged spaced from thevalve bodies and the supporting can be effected via a hydraulic fluidwhich in turn is supported by the gas spring, for example in a pressurecan.

For sterilization of the sterile material received by a sterilizingcontainer in a steam sterilizer the following valve functions arenecessary, as already mentioned:

1. Influx valve: Through this valve the steam serving for thesterilization must be introduced into the container interior.

2. Vacuum valve: Through this valve the air originally located in thecontainer and subsequently the steam mixed with the residual air must beextracted from the container.

3. Condensate drain valve: Through this valve the condensate which hasformed in the container, for example in the sterilization of(non-porous) instruments, is to be drained.

The various valves similar in their basic function in the examplesillustrated can each carry out several functions. However, generally itwill be expedient to provide several valves in the cover or in thebottom and to assign to each of said valves only one or at the most twofunctions. Hereinafter the mode of operation of the individual valveswill be described with regard to their preferred use but this does notexclude any use for a different purpose.

The valve according to FIG. 3 is primarily suitable as influx oradmission valve and in this function is conveniently suspended on thewall portion 32 formed as cover or intermediate cover on the inner sideof the container.

Before introduction of the sterilizing container into the sterilizer thevalve is closed by the bias of the spring 44 and possibly by the bias ofthe gas pressure chamber 24. The gas pressure chamber is filled with airunder atmospheric pressure (i.e., ambient pressure). Fluctuations in theatmospheric pressure do not appreciably affect the operation of theinvention. In the initial single or repeated extraction of air or thesteam-residual air content in the vacuum phases 1-2-3 (FIG. 12) thevalve remains closed because the atmospheric pressure within the chamber24 is positive with respect to the external pressure and is furtherincreased by heat. In the now following steam admission phase 3-4 thevalve is opened, this being done at a point somewhat above atmosphericpressure because of the bias of the spring and possibly because of thepressure increase due to the temperature increase. However, in contrastto conventional check valves the valve according to the invention doesnot close at the position 4 of maximum pressure but remains open overthe entire sterilizing phase 4-5 because the gas chamber remainscompressed due to the externally obtaining excess pressure. When thepressure drops between 5 and 6 (FIG. 12) the valve still remains openuntil at a point somewhat above atmospheric pressure (due to the springbiasing and heating of the air within the chamber) the valve againcloses. In the subsequent vacuum phase 6-7-8-9 the valve remains closed.

FIG. 4 shows a valve according to the invention in a typicalconstruction and use as vacuum valve. In this case the chamber wall 38together with the stiffening plate 40 is secured to the one part of thecontainer portion 32 forming the container cover. The stiffening plate36 bearing in this case externally on the opposite chamber wall 28extends with an annular edge 48 outwardly and bears on a sealing ring 50which is inserted into a U-profile 52 fixed on the container cover. Thebiasing spring 44' bears on the plate 36 and on the valve housing 46.

In all the FIGS. the letter I denotes the container interior and theletter A the space disposed outside the sterilizing container (in theautoclave) (this applies to the preferred use described; a reversal isconceivable for modified construction or modified use).

In the rest state the valve according to FIG. 4 is closed by the bias ofthe spring 44'. After compensation of the spring bias the valve 4 opensin the vacuum phase just below the atmospheric line and remains openduring the entire vacuum phase 1-2-3, the setting preferably being suchthat the open position is also retained when the internal and externalpressures in the vacuum region are equal. During the excess pressurephase 3-4-5-6, in which the sterilization takes place, the valve remainsclosed due to the externally obtaining excess pressure and opens againin the vacuum phase 6-7-8-9.

FIG. 5 shows the invention applied to a typical condensate drain valve.In this case the valve is fixed to the inner side of the wall portion 32formed by the container bottom 15. The condensate drain valve accordingto FIG. 5 remains in the open position as long as the pressure outsideof the chamber 24 is higher than the starting pressure within thechamber, i.e. during the entire sterilizing phase 3-4-5-6 and not onlyduring the influx or admission phase 2-3-4 as is the case with an excesspressure or pressure-limiting check valve. Compared with a bi-metaldrain valve the advantage is achieved that the valve according to theinvention operates independently of the temperature conditions and has alarge stroke and higher application pressure.

The design according to FIG. 6 permits use as influx valve and in thiscase the valve is mounted externally on the cover 14. To ensure openingwhen the outer pressure rises a radially outwardly projecting pressureface 54 is provided with which the outer pressure raises the valve body30 and when a sealing gap has been formed the outer pressure can engagethe entire wall face 28. Otherwise the function is as described inconjunction with FIG. 3.

If the valve according to FIG. 6 is to be used as condensate drain it isinserted into the container bottom 15 in the manner described and thenoperates in the same manner as the valve described in conjunction withFIG. 5.

FIGS. 7 to 11 illustrate some further modified examples valves accordingto the invention which operate in the arrangement illustrated as steamadmission valve. However, on corresponding modification use ascondensate drain valve is also conceivable.

The valve 7 has the particular feature that the container wall 32 isprovided with an inwardly projecting edge 56 which surrounds the valvebody rib 30. The outwardly lying pressure face 54 which effects theinitial raising is not beveled as in the example of embodiment of FIG. 6but made stepped. The container wall is also provided radially outsidethe valve body 30 with an inwardly drawn rib 58. In the embodimentaccording to FIG. 8 said latter portion is made planar and a bean 30' isprovided instead of the valve body rib.

In addition, in the examples according to FIGS. 5 and 9 the valvehousing wall forms at the same time the outer boundary of the gaschamber 24.

The embodiment of FIG. 10 differs from the remaining examples in thearrangement and configuration of the encircling annular wall. In theembodiment of FIG. 11 the chamber wall extends outside the valve bodyrib 30 in the plane of the cover and perpendicularly thereto, aresilient bead 60 being formed therebetween.

FIG. 12 shows the time-dependent pressure variation P within thesterilizing container and the valve functions. The step-like form of thecurves in the region of the zero passage is due to the valve biasing,i.e. by the spring pressure and possibly by the gas pressure within thegas pressure chamber.

The sterilizing operation includes the following phases: single ormultiple vacuum phase (1 to 3), to excess pressure phase (3 to 6) withsterilizing phase (4 to 5), after-vacuum phase (5 to 8) ventilationphase (8 to 9). In contrast to known devices the valve effective in eachphase is also kept open after reaching the negative or positive peakpressure value until the pressure in the autoclave has adjusted itselfto a predetermined closure switching pressure (3', 6', 9'). In addition,the valve effective in each phase is kept closed until the pressure inthe autoclave has adjusted itself to a predetermined opening switchingpressure (1", 3", 6"). The absolute values of the opening switchingpressure and closing switching pressure are conveniently made of equalmagnitude.

According to the examples illustrated the valves are controlled independence upon the pressure obtaining in the autoclave.

Alternatively or additionally the valve control can also take place intime dependence on the pressure zero passages (atmospheric pressures) inthe autoclave or in dependence upon the temperature obtaining in theautoclave. A sensor initiating the switching function may be associatedwith each valve arrangement. Finally, it is also possible to control thevalve arrangement externally.

FIG. 13 shows a double valve which can be used as admission or influxvalve or as vacuum valve and furthermore also as condensate drain valve.The valve body 82 cooperating with a valve seat 64 of the container wallportion 32 is biased by a spring 66 into the closure position. The valvebody 62 is guided with a cylindrical extension 68 on a bush 70 which iscarried via a holder 72 by the container wall 32. The valve body 62carries an actuating member 74 which has a frusto-conical head 76. Thegas chamber is surrounded by a bellows 78 which is hermetically sealedand connected at one end to a container-fixed block 80. The other end ofthe bellows 78 is secured to a thrust rod 82 which is axiallydisplaceably guided in bearing blocks 84. In the region of the actuatingmember 74 the thrust rod 82 comprises a turned-down portion which isdefined by two conical faces 86 and an intermediate cylindrical portion88.

FIG. 13 shows a center position in which the valve is closed. If theouter pressure increases the bellows 78 is compressed and the thrust rod82 displaced to the right according to FIG. 13. As a result the valve isopened via the conical slide faces 86 and 76.

If however starting from the center position according to FIG. 13 thepressure drops then the bellows 78 expand and the thrust rod 82 isdisplaced to the left so that the valve also opens.

The axial length of the cylindrical portion 88 is somewhat greater thanthe diameter of the head end 76 so that a certain idle movement isincorporated and as a result the valve remains closed within apredetermined pressure difference range.

Accordingly, the valve illustrated in FIG. 13 can perform all the valvefunctions because it is controlled by the bellows 78 both in the vacuumregion and in the excess pressure region.

In all the examples the gas chamber may be set to the particularatmospheric pressure. For this purpose a vent or ventilation valve notshown in the drawings may be provided and permits pressure equalization.However, generally outer weather-induced air pressure fluctuations neednot be taken into account and it suffices to provide a pressureequalization to the corresponding altitude where the container is to beused. For this purpose an opening can be provided which can bepermanently sealed by a resilient stopper.

In the embodiment illustrated in FIG. 13 the actuating means 78, 82, 86,88 is secured to the container wall via the bearing blocks 80, 84.However, the invention also covers the case of separating said actuatingmeans from the valve and arranging said means detachably so that theactuating means is connected to the valve only in the sterilizer and thesterilizing container (outside the sterilizer) can be transported andstored without said actuating.

Although the present invention has been described in connection withparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention be limited not by thespecific disclosure herein, but only by the appended claims.

In the claims:
 1. The method of sterilizing material within anautoclave, comprising the steps of:locating the material within acontainer, the container including a vacuum valve and an admissionvalve; locating the container within the autoclave; thereafter reducingthe pressure within the autoclave from a starting pressure to a firstnegative peak pressure and thereafter increasing the pressure within theautoclave from the first negative peak pressure to the startingpressure; opening the vacuum valve while reducing the pressure withinthe autoclave from said starting pressure to said first negative peakpressure, keeping the vacuum valve open while the pressure within theautoclave is at the first negative peak pressure and closing the vacuumvalve while increasing the pressure within the autoclave from said firstnegative peak pressure to said starting pressure; thereafter increasingthe pressure within the autoclave from the starting pressure to apositive peak pressure and thereafter reducing the pressure within theautoclave from the positive peak pressure to the starting pressure;opening the admission valve while increasing the pressure within theautoclave from the starting pressure to the positive peak pressure,keeping the admission valve open while the pressure within the autoclaveis at the positive peak pressure and closing the admission valve whilereducing the pressure within the autoclave from the positive peakpressure to the starting pressure; thereafter reducing the pressurewithin the autoclave from the starting pressure to a second negativepeak pressure and thereafter increasing the pressure within theautoclave from the second negative peak pressure to an end pressure; andopening the vacuum valve while reducing the pressure within theautoclave from the starting pressure to the second negative peakpressure, keeping the vacuum valve open while the pressure within theautoclave is at the second negative peak pressure and closing the vacuumwhile increasing the pressure from the second negative peak pressure tothe end pressure. wherein the vacuum valve includes a sealed chamberwhich expands and contracts according to the pressure within theautoclave, wherein reducing the pressure within the autoclave from thestarting pressure to either the first or second negative peak pressurecauses the chamber to expand and thereby open the vacuum valve, whereinmaintaining the pressure within the autoclave at either the first orsecond negative peak pressure keeps the chamber expanded and therebykeeps the vacuum valve open and wherein increasing the pressure withinthe autoclave either from the first negative peak pressure to thestarting pressure or from the second negative peak pressure to the endpressure causes the chamber to contract and thereby close the vacuumvalve.
 2. The method of claim 1, further comprising the step ofmaintaining the pressure within the autoclave at the positive peakpressure for a predetermined period of time.
 3. The method of claim 1,wherein the admission valve includes a sealed chamber, wherein the stepof increasing the pressure within the autoclave from the startingpressure to the positive peak pressure causes the admission valvechamber to contract and thereby open the admission valve, wherein a stepof maintaining the pressure within the autoclave at the positive peakpressure keeps the admission valve chamber contracted and thereby keepsthe admission valve open and wherein the step of reducing the pressurewithin the autoclave from the positive peak pressure to the startingpressure causes the admission valve chamber to expand and thereby closethe admission valve.
 4. The method of claim 1, wherein the vacuum andadmission valves are defined by a single valve means.
 5. The method ofclaim 1, wherein the container further includes a condensate valve, themethod including the steps of opening the condensate valve whileincreasing the pressure within the autoclave from the starting pressureto the positive peak pressure, keeping the condensate valve open whilethe pressure within the autoclave is at the positive peak pressure andclosing the condensate valve while reducing the pressure within theautoclave from the positive peak pressure to the starting pressure. 6.The method of claim 5, wherein the step of opening the admission valveprecedes the step of opening the condensate valve and the step ofclosing the condensate valve precedes the step of closing the admissionvalve.